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https://issues.apache.org/jira/browse/IGNITE-19900?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alexander Lapin updated IGNITE-19900:
-------------------------------------
Epic Link: IGNITE-19902
> Server nodes should both propagate and handle HLC timestamps to/from clients
> within tx RW protocol
> --------------------------------------------------------------------------------------------------
>
> Key: IGNITE-19900
> URL: https://issues.apache.org/jira/browse/IGNITE-19900
> Project: Ignite
> Issue Type: Improvement
> Reporter: Alexander Lapin
> Priority: Major
>
> h3. Motivation
> RW TX protocol requires commit timestamp to be greater than all other
> timestamps associated with previous TX actions of the same transaction. For
> more details, please check
> [IEP-91:Hybridlogicaltime|#IEP91:Transactionprotocol-Hybridlogicaltime].].
> Thus, any TX request/response up to the commit timestamp generation transfers
> a hybrid timestamp from one TX actor to another, where another actor adjust
> its HLC as
> {code:java}
> max(requestTime.longValue() + 1, max(now, oldLatestTime + 1));{code}
> See
> {code:java}
> org.apache.ignite.internal.replicator.message.TimestampAware{code}
> and
>
> {code:java}
> org.apache.ignite.internal.hlc.HybridClockImpl#update{code}
> for more details.
> Given logic was already implemented for server-side communication and thus
> should only be expanded to the client side, so that clients can route TX
> requests themselves for the best-effort affinity purposes. It is worth to
> mention that client won't have HLC instance itself, because it's not possible
> to cover clients with clock skew management, thus it will only store
> timestamp received from the server and send it back with RW/RO requests.
> Client-server protocol adjustments (adding hybridTimestamp field to both
> requests and response together storing logic) will be implemented in
> https://issues.apache.org/jira/browse/IGNITE-19884 along with propagating
> commitTimestmap and RO.readTimestamp to the client, meaning that withing
> current ticket it'll be necessary:
> * To expand list of such server-to-client TX-related timestamp producers, in
> a way that *all* RW TX responses, that were triggered from client, will
> propagate corresponding response timestamps to a client.
> * Timestamp retrieved from the client wihtin the scope of RW TX flow will
> adjust server HLC.
> h3. Definition of Done
> * The HLC adjustment on the server actors of the RW TX protocol is also
> available in cases of their communication transitively through the client.
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